Crack with Speedball. I built it and enjoyed it. Please note the ding on the top left of the base. Picture four is a close-up. A fun, enjoyable headphone amp. The Crack is designed for use with high impedance headphones and it paired well with my Sennheiser HD600s. I thought it sounded especially good with the Tung-Sol 5998 that I'm including in the sale. I bought it NOS with closely matched sections. The tube has a few hundred hours on it, but still sounds great. Also included are two input tubes, both 12AU7 variants, a GE 5814A and a Sylvania 6189, both 60s vintage. Price includes PayPal and shipping via FedEx.